1. Technical Field
This invention relates generally to Emergency Call Services. More particularly, this invention relates to a method and network to provide mobile for emergency calls based on mobile station position during a call in progress.
2. History of Related Art
The increase in emergency calls made by mobile subscribers has led to the development of several telecommunications standards for Emergency Call Services such as J-STD-036, “Enhanced Wireless 9-1-1, Phase 2” drafted by the American National Standards Institute (ANSI) and the Telecommunications Industry Association (TIA), incorporated herein by reference in its entirety. The J-STD-036 standard utilizes the concept of positioning for tracing the location of an emergency call. One problem that exists with this tracing method is that the emergency location which actually needs to be provided to the emergency center is frequently not equivalent to the location of the telephone placing the Emergency 911 (E-911) call. Moreover, position location under the current method requires many signaling messages to be sent over the telecommunications network between the different entities, delaying connection with the emergency center. For example, during a routine call between an A-Subscriber and a B-Subscriber, assume an unexpected emergency situation arises involving the A-Subscriber. Under the prior art scenario, if the A-Subscriber's conversation with the B-Subscriber is interrupted, the B-Subscriber knows that something is wrong, places the call with the A-Subscriber on hold, and dials 911 to contact an emergency service provider communicating through an Emergency Services Network Entity (ESNE). Under the current position location method, the B-Subscriber's location will be calculated since the B-Subscriber triggered the call, while A-Subscriber is the party requiring emergency assistance.
Currently, the J-STD-036 solution is based on a positioning request to the Anchor Mobile Switching Center (MSC), which is transmitted to the Anchor Mobile Position Center (MPC) for mobile capabilities and position request type. Since the Mobile Station (MS) is not served by the Anchor MSC, the request is sent back to the Anchor MSC which forwards the request to the Serving MSC. The Serving MSC, in turn, requests the cached position from the Serving MPC, which will request the position from its Position Determining Entity (PDE) for the current E-911 call. Once the PDE provides the position to the serving MPC, it is transmitted to the Serving MSC. Then the position is transmitted to the Anchor MSC as a return result for the requested order. The Anchor MSC then supplies an answer to the initial position request from the Anchor MPC, which finally provides the geographic position of B to the Anchor MSC in order to make the call setup with the ESNE.
Several problems may arise in this scenario. A considerable amount of time and a significant number of network messages are required for the Anchor MSC to set up the emergency call to the ESNE. While all this occurs, several additional events may arise, such as network congestion, handoff to a third party, or other unexpected situations at the MS, such as a low battery condition. This may result in tragic consequences because of the emergency nature of the call. What is needed is a method and network which will give the emergency services provider accurate information regarding the true location of the emergency using a minimum number of network messages.